Which of the following is NOT a focus of NTSB investigations?

The National Transportation Safety Board (NTSB) primarily focuses on investigating transportation accidents, determining their causes, and recommending measures to improve safety. Offering pilot certifications does not fall within the scope of their mandate. This function is typically the responsibility of regulatory agencies such as the Federal Aviation Administration (FAA) in the United States. The NTSB's role is to analyze accidents and incidents to gather insights that can inform safety improvements, rather than certify individuals to operate aircraft.

Determining causes of accidents and making safety recommendations are central to the NTSB's mission. Additionally, analyzing missed communication incidents is closely related to accident investigations, as communication breakdowns can often be a contributing factor in accidents. Thus, the correct answer highlights a key distinction between NTSB responsibilities and other aviation regulatory roles.